Working Out May Boost Immune Responses via CD8+ T Cells

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Are you feeling unmotivated to work out regularly during the COVID-19 pandemic? Do you need a fresh source of daily motivation to stick with an exercise regimen involving cardio and strength-training workouts?

If so, consider this: Accumulating evidence suggests that both aerobic exercise and muscle-building workouts activate CD8+ T cells in a way that makes the immune system stronger.

Earlier this year, a mouse study (Wu et al., 2020) by researchers from the German Cancer Research Center identified a correlation between increased lean muscle mass, less antiviral CD8+ T cell exhaustion, and more robust immune responses. These findings were published on June 12 in Science Advances. (See "Can Building Muscle Mass Fortify the Strength of T Cells?")

Now, a new study (Rundqvist et al., 2020) from the Karolinska Institute in Sweden reports that "running mice" who were allowed to exercise voluntarily on running wheels in their laboratory habitat activated their CD8+ T cells in ways that made their immune response more potent and mediated exercise-induced reductions in tumor growth. These findings were published on October 23 in eLife.

In addition to using animal models, the Swedish researchers also investigated how exercise-induced metabolites changed in human study participants after a vigorous aerobic workout. Notably, Rundqvist et al. found that a single 30-minute bout of endurance exercise on an indoor bicycle altered the immune-boosting metabolic profile of human plasma in ways that mirrored animal models.

"We show here that in mice, exercise-induced reduction in tumor growth is dependent on CD8+ T cells, and that metabolites produced in skeletal muscle and excreted into plasma at high levels during exertion in both mice and humans enhance the effector profile of CD8+ T cells," the authors explain. "These data demonstrate that CD8+ T cells are metabolically altered by exercise in a manner that acts to improve their antitumoral efficacy."

"Our research shows that exercise affects the production of several molecules and metabolites that activate cancer-fighting immune cells and thereby inhibit cancer growth," first author Helene Rundqvist of the Karolinska Institute's Department of Laboratory Medicine said in an October 26 news release. "We hope these results may contribute to a deeper understanding of how our lifestyle impacts our immune system and inform the development of new immunotherapies against cancer."

"The biology behind the positive effects of exercise can provide new insights into how the body maintains health as well as help us design and improve treatments against cancer," corresponding author Randall Johnson of Karolinka's Department of Cell and Molecular Biology added.

The current physical activity guidelines (Piercy et al., 2018) recommend a combination of moderate-to-vigorous physical activity (MVPA) for about 30 minutes per day, most days of the week (equaling at least 150 minutes per week of cardio), along with at least two muscle-strengthening workouts per week. (See "New Physical Activity Guidelines Based on Decade of Research.")

Previous all-cause mortality studies (Zhao et al., 2020; Gebel et al., 2015) have shown that sticking to these recommended physical activity guidelines promotes longevity and reduces the risk of premature death. Why is this? According to the latest (2020) research, one reason may be that the combination of cardio workouts and weight lifting exercises that increase lean muscle mass strengthen the immune system via exercise-induced metabolites that activate CD8+ T cells.